Various methods of molding hollow plastic articles and/or containers are well known in the prior art. Plastiic containers have found substantial increasing applications, however, despite their weight and toughness, their use is restricted by the cost and characteristic of the plastic composition, particularly for storage of products which will deteriorate or be contaminated, inter alia, by water, carbon dioxide, oxygen and the like.
Recently a process has been advanced which produces a barrier container, i.e., a semi-rigid plastic container provided with a liner or inner layer of another material having properties different than the other layer thereof. In accordance with such process, a preformed liner or sleeve (manufactured, for example, by thermoforming techniques) is positioned over a core rod with a parison being subsequently formed about the liner in an injection station of an injection blow molding machine. The lined parison is thereafter expanded in a blow molding station of the machine with the resulting lined container being removed from the core rod in a product receiving station.
In a commercial rotary injection blow molding assembly, there is provided a plurality of core pins at each location of the rotating platen, as more fully hereinafter described. Consequently, at operational speeds of such a machine, it is necessary to position successively a single liner on each of the core pins prior to parison forming to minimize the manufacture of an unlined container (with attendant problems of sensing an improperly formed container), as well as to reduce the deleterious effect on an unlined core rod cycling through the parison forming and blow molding stations, which could produce unacceptable lined containers for a few subsequent cycles.